1. Field of the Invention
The present invention relates to a sampling point generating apparatus for generating sampling points on an original curve and forming a cubic curve that approximates the original curve.
Output units such as displays and printers are required to provide high-quality outputs. One method of providing high-quality character outputs is to employ outline fonts that express each character as outlines.
Outline fonts usually employ spline curves and Bezier curves represented by cubic expressions. Sampling points to form a cubic curve are obtained on an original curve through complicated calculations such as spline smoothing calculations. These calculations take time and reduce the processing speed. There is a technique for finding sampling points on an original curve according to the angle of each vector on the original curve but the quality of cubic curves provided by this technique is poor. It is thus required to provide a sampling point generating apparatus that speedily generates sampling points to form a cubic curve that precisely represents a character outline.
2. Description of the Related Art
A sampling point generating apparatus according to a prior art calculates an angle formed between straight lines that pass through adjacent coordinates on an original curve, and if the angle exceeds a given threshold, generates sampling points at the coordinates. The start and end points of the original curve also serve as sampling points. The coordinates of the sampling points are stored in a memory. The sampling points are interpolated to provide a curve that approximates the original curve.
This approximate curve does not include gentle slope portions contained in the original curve. This problem occurs because the prior art generates the sampling points according to angles formed by straight lines and discards small angles below a threshold, so that no sampling points are formed on the gentle slope portions.